Flaw size maximum

Example 2.22 A certain grade of acrylic has a Kc value of 1.6 MN and the fatigue crack growth data as shown in Fig. 2.77. If a moulding in this material is subjected to a stress cycle which varies from 0 to 15 MN/m, estimate the maximum internal flaw size which can be tolerated if the fatigue endurance is to be at least 1(P cycles. 

In contrast, the burst pressure or the required fracture toughness of steel or weld can be estimated when the maximum flaw size or the desired MAOP are given, respectively. The pipeline parameters used for the calculation are shown in Table 10.2. The flaws for the calculation are assumed to be semiellipse with the depth-to-length ratio of 1 10. 

It is most unlikely that matrix grain refinement alone can explain the high fracture strengths that have been reported. Using the reported maximum fracture strengths (o = 1100 MPa)12 and the nominal fracture toughness of alumina (A"Ic = 3.5 MPa.m1/2), the critical flaw size, (c), can be estimated from... 

As can be seen in Fig. 10 [29], the fracture toughness in poly crystalline tetragonal zirconia (TZP) and partially-stabilized zirconia (PSZ) appears to reach a maximum. This indicates a transition from flaw-size control of strength to transformation-limited strength. Ranges of fracture toughness values for zirconia composites are given by Richerson [38]. 

A soda-lime silica plate failed at 100 MPa. (a) Estimate the flaw size and state any assumptions you make, (b) If the plate were made of fused silica and contained the same flaw size what is the maximum applied stress it could withstand without breaking Assume the glass has T = 70GPa. 

Ceramic Maximum flaw size (tim) Average flaw size (lim)... 

VI.36. The reference flaw of 6 1 aspect ratio should have an area, normal to the direction of maximum stress, greater than typical pre-service inspection indications that might be cause of rejection or repair of a fabricated packaging containment wall. However, since the reference flaw is a crack-like surface defect, rather than a more typical real defect (e.g. subsurface porosity cloud or slag inclusion), the selection of this flaw size is extremely conservative relative to workmanship standards. 

MDF materials exhibit a relatively small but distinct porosity (Alford et al 1982 Poon and Groves, 1987 Silsbee et al, 1991b Young, 1991 Igaiashi and Takaheshi, 1992 Roy, 1992). In general the porosities found in Portland cement based MDF materials are larger than those of calcium aluminate cement based products. From mercuiy porosimetiy values of up to 20 vol.% have been reported for the former and below 5 vol.% for the latter. Values found by nitrogen adsorption are usually very low. The maximum flaw sizes in MDF materials are reduced typically to 10-100 //m (Russell et al, 1991). 

During the Monte Carlo sampling process, the sampled values of OTnotcu), fluence, Cu, Ni, P, and Mn are used to compute a sampled value of ATso using the relationships in Table 12.1. The flaw depths are deterministic and are defined in increments of 1/100 of the vessel wall thickness, while the number of flaws in a vessel and the flaw aspect ratios are sampled from distributions. The maximum value of cpi obtained from Eq. 12.6 for a specific transient and flaw size is the CPI for that transient and flaw size. 

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